In mobile telephone networks, communication based on fixed wireless access (FWA) using millimeter waves is widely used. Communication quality of a wireless link is affected by a wireless environment such as a signal to noise ratio (SNR) of a received signal. Accordingly, in order to realize a wireless link having a broader band, adaptive modulation technology is being focused on.
The adaptive modulation technology is technology which adaptively finds and employs a modulation scheme with which transmission efficiency is best from a wireless state of a wireless link. Because it is possible to perform the optimum wireless communication corresponding to a wireless environment if the adaptive modulation technology is used, expectations for the adaptive modulation as technology for improving frequency efficiency have increased.
However, because a link bandwidth varies with the passage of time in the case of the above-described wireless link, it is difficult to efficiently perform bandwidth allocation for traffic flowing through the same link. It is to be noted that if bandwidth control or priority control such as the bandwidth allocation is not performed, traffic having the largest traffic amount at that time is likely to monopolize a bandwidth. Consequently, a problem to be solved is how to control bandwidth allocation among traffic.
Incidentally, in DiffServ, asynchronous transfer mode (ATM), or the like, bandwidth control is performed using a committed information rate (CIR), which is a bandwidth in which minimum traffic can be maintained even during congestion. Thereby, it is possible to fairly perform bandwidth allocation among traffic having the same priority to a certain extent. It is to be noted that a bandwidth allocation method depending on the magnitude of the CIR is proposed in Non-Patent Document 1.
In addition, Patent Document 1 discloses a method for allocating a bandwidth at a constant rate as a method for allocating a bandwidth to traffic in a link such as a wireless link in which the bandwidth fluctuates.
Further, the following method is disclosed in Patent Document 2. That is, when a wireless link uses a modulation scheme that provides a minimum transmission rate for a bandwidth required by traffic, it is first determined whether or not the required bandwidth can be allocated, and the required bandwidth is allocated to the traffic if the required bandwidth can be allocated. Thereafter, if the wireless link uses a modulation scheme that provides a higher transmission rate, an extra bandwidth is allocated to best-effort traffic, which does not require bandwidth guarantee.